Within an UMTS (Universal Mobile Telecommunications System) system the service combination and data rate selection format used to combine transport channels into a physical data stream coded composite transport channel is called transport format combination. For adaptation of occupied transmission resources to rapidly changing service requirements, the transport format combination (TFC) used by one transmitter may change rapidly. For decoding data (overhead and payload) at the receiver, the receiver must know the actually used channel format. Therefore, a transport format combination indicator (TFCI) may be attached to each frame of data to indicate which TFC has been selected. The receiver uses the TFCI to select the format for a decoding and separation of data into the different services.
For saving the bandwidth required for the TFCI, a Blind Transport Format Detection (BTFD) method has been suggested. This is a scheme for detecting (e.g. at the receiver side) the format of the transport channels. In case a data block is terminated by an error detection code, e.g. a CRC (Cyclic Redundancy Check) code, a test is performed to check whether a given sequence of bits in a data stream could be a CRC code for a block of data bits preceding the CRC bits. BTFD may make use of this fact. One concept of BTFD supposes the existence of following five types of transport channels: dual transport channels, explicit transport channels, DTF transport channels, guiding transport channels, and guided transport channels.